<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>盒子模型</title>
    <style>
      /*  .box {
            width: 400px;
            height: 400px;
            background-color: greenyellow;
            border: 1px solid;
            padding: 20px;
            margin-left: 300px;
            margin-top: 100px;
            !* border-left: 1px solid;*!!*left right top bottom*!
        }*/

        .box{
            border: 1px solid;
            background-color: greenyellow;
        }

        .box1{
            width: 100px;
            height: 100px;
            margin-bottom: 15px;
        }

      .box2{
          width: 100px;
          height: 100px;
          margin-top: 10px;
      }

    </style>
</head>
<body>
<div class="box box1">
  hello world !
</div>

<div class="box box2">
    hello world !
</div>
</body>
</html>